An engine may include an evaporative emissions system for reducing an amount of fuel vapor that may escape from a vehicle. The evaporative emissions system may capture fuel vapors while the vehicle is parked and not operating, while the vehicle is being refueled, and while the vehicle is being operated. The vehicle may trap fuel vapors in a fuel vapor storage canister for subsequent introduction to the engine after the engine is started.
Regulatory agencies may require monitoring the evaporative emissions system to ensure its proper operation as the vehicle is used. One way to monitor the evaporative emissions system is to apply a vacuum to the evaporative emissions system and determine if the system leaks by more than a threshold amount over a specified period of time. However, leak checking the evaporative emissions system may not be as comprehensive as is desired to ensure proper evaporative emissions system operation. Therefore, it may be desirable to provide a more comprehensive method for establishing whether or not an evaporative emissions system is operating as is desired.
The inventor herein has recognized the above-mentioned predicament and has developed a method, comprising: responsive to selected conditions, commanding close a fuel vapor blocking valve while opening a canister vent valve and a canister purge valve; indicating a degradation of the canister vent valve or the canister purge valve responsive to a fuel vapor flow not decreasing while the canister purge valve is exposed to a threshold vacuum; and adjusting an actuator in response to indicating the degradation.
By commanding selected valves to predetermined operating states, it may be possible to provide the technical result of determining degradation of individual evaporative emissions system components in response to fuel vapor flow. For example, if a fuel vapor barrier valve is commanded closed along with commanding a canister purge valve open and a canister vent valve open, it may be determined that the canister purge valve is in a stuck closed position if fuel vapor flow does not decrease.
The present description may provide several advantages. In particular, the methods may identify degradation of individual emission systems components. Further, the methods may be implemented using existing sensors and actuators. Further still, mitigating actions may be taken if degradation is determined so that fewer evaporative emissions may be released to the atmosphere.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.